Quick Question

A 4 kg block, traveling at 6 m/s on a horizontal surface collides with an identical 4 kg block that is motionless in a perfectly inelastic collision. The combined masses then collide head on with a third 4 kg mass which is at rest. If the larger mass continues with a velocity of 1 m/s, what is the velocity of the third 4 kg mass if the final collision was elastic?